JP5502262B2 - Method and apparatus for obtaining geodetic distance data - Google Patents

Abstract

A method for extracting geodetic/geodesic distance/ranging information with a signal generator for generating at least two HF modulation frequencies in the MHz- up to the GHz-range requires a system with a system-input, an optical radiation source, at least one target object (3a, 3b) and a receiver (4'') with a system output and an analysis/evaluating electronics. Initially, the system is excited with at least two, especially synthetic, modulation frequencies, preferably a group of discrete modulation frequencies, by applying at least one excitation signal at the system input. At least one system response is picked up at the system output and distance /ranging information is derived from the signal shape of the system response by the analysis electronics. Independent claims are included for (a) a device for carrying out the method, for (b) a geodetic/geodesic measurement instrument, especially a theodolite, for (c) a scanner for three-dimensional image-scanning and for (d) use of the device.

Description

  The present invention provides a method and apparatus for obtaining geodetic distance data described in the premise of claims 1 and 23, a geodetic instrument described in claim 29, a scanner described in claim 31, and a claim 32. To the method of using the device described in.

  Distance measurement is a technical task in which many solutions for optical systems are used. The tachometer is a classic surveying instrument for surveying work for the geodetic and construction industries. Recently, there has been an increase in the provision of tachometers with a reflectorless telemetry device (EDM).

  Initially, the surveyed range was 60 m, but the demand for surveying range is steadily increasing due to the increased use of equipment. Today, surveying instruments can measure up to 200m without reflectors.

  Traditional telemetry devices are mainly based on the principle of time of flight or phase contrast. High-precision surveying in the mm range is required, and today most instruments are equipped with EDM according to the phase measurement principle. They are also useful for distance measuring theodolites because of their smaller dimensions.

  However, due to the low-light signal of the target that does not reflect, the phase meter has a small measurement range, and it is almost impossible to measure without a reflector with respect to a distance of 300 m or more by the phase meter. On the other hand, the distance measuring time meter is more advantageous than the phase meter in the distance range. This is because it is easy to measure a distance exceeding 500 m of a target without a reflector. However, the distance measuring time meter has a drawback that the absolute measurement accuracy of 1 mm cannot be substantially achieved. An overview of the various methods and devices for ranging is described in the 1999 distance and direction electronic measurement method (M. Joeckel and M. Stober, 4th edition, by Verlag Konrad Wittwer and Stuttgart). .

  With the expansion of the introduction and use of reflectorless telemetry devices in measurement stations, users often encounter another problem primarily arising from the use of these reflectorless devices. In particular, in the case of relatively large measurement distances, special targets, or in particular background terrain, the measurement beam emitted from the telemetry device may hit two targets simultaneously. One example of this problem is, for example, when measuring the edge of a table. When this edge is measured, some part of the beam hits the edge to be measured, while the other part of the beam passes through the target and illuminates other objects behind or on the floor. Yet another example is where there is a reflector near a weakly reflecting target, and the scattered light enters the receiver of the telemetry unit via the reflector. Therefore, the conventional phase meter leads to calculation of an incorrect distance that does not correspond to any of the targets. In particular, when reflectorless distance measurement is used for long distances, the possibility of measuring an unintended object between the actual survey target and the instrument increases. Another typical case is when measuring distance through trees or knitted fences. Applying no reflector can lead to serious mismeasurements due to the frequency of the dissipated light of the obstacle. Therefore, it has been studied to estimate a correct distance in a situation where a plurality of objects are simultaneously irradiated with a measurement light beam.

  The measuring light reflected and dissipated by natural objects is extremely weak, especially at long distances. In this connection, a difficult case is distance measurement in rain, fog, and snowfall, and particles falling in the air act as an additional target with a soft surface. Depending on the amount of rainfall, the interference affects the actual distance measurement. For example, in the case of heavy rain, erroneous measurement values cannot be excluded.

  In addition, the phase meter cannot accurately measure a plurality of targets, resulting in further difficulty. In the received signal, phases of a plurality of targets are superimposed and cannot be separated, and components of each target cannot be clearly separated by the phase difference method. In particular, in the case of fog, rain, and snowfall, there is a possibility of erroneous measurement.

  Telemetry devices based on the time-of-flight method (ranging time method) belong to the most powerful telemetry devices. The range of unreflected targets is particularly excellent, and multiple targets can be measured in principle. On the other hand, one of the main drawbacks of this distance measuring method is that the accuracy of distance measurement is poor and the apparatus is complicated. Recent ranging time meters are also poor in heavy rain or dusty air. One reason for this is that the low frequency components of the pulse signal are applied, which are reliably inaccurate by dust or airborne particles.

  Another disadvantage of this ranging time method is caused by the laser source. Pulse laser devices that produce good quality beams are, for example, solid state or microchip laser devices that are expensive and complex in terms of control and power consumption. Although semiconductor lasers are economical, their three-dimensional coherence is reduced or lacking and is currently unsuitable for beam quality. Recently, there are no diode range finders that provide a laser beam at a small measurement point. Therefore, for example, the distance to the outline such as the edge of the object cannot be measured accurately using a telemetry device based on a semiconductor laser.

  The distance range of the target without reflector and the insufficient accuracy of the measurement are fundamental drawbacks of all currently known surveying principles.

  Yet another disadvantage is that the capability for multiple goals is not technically realized. In geogrammetry, there is no known telemetry device that can reliably distinguish between multiple targets and reliably measure different targets.

  Therefore, an object of the present invention is to provide a novel distance measuring method and a device suitable for the method, and for long distances, thereby enabling reflectorless distance measurement and high accuracy in mm. Enable measurement.

  Another object of the present invention is to enable accurate ranging of multiple targets.

  Yet another object of the present invention is to reduce the effects of common atmospheric influences, such as dust or smoke, so that accurate ranging is not affected by them.

  Yet another purpose or need to be met allows for short ranging times in seconds and can accommodate special weather conditions such as fog, rain, or snowfall, and is incorporated into ranging systems such as theodolites Is possible. This ease of installation depends on miniaturization or structure, module design, and energy saving consumption.

  These objects are achieved by the present invention, i.e. by the features of claims 1 and 23 and the features of the dependent claims, and solutions can be developed.

  The solution is based on the concept of an electro-optic telemetry device according to the principle of “system analysis”. It is not a pure ranging meter or a pure phase meter. The ranging system includes an element that emits an optical signal, a ranging distance of at least one target, optionally a reference distance within the device, and an element that receives the element. This system is provided to each case through each interface that functions as a system input and output. A telemetry device consisting of a transmission / reception unit together with a measurement distance and a target is understood as a transmission system for optoelectronic signals. For simplicity, this system is hereinafter simply referred to as the system. Thus, the target is part of the system. This system is analyzed by the method of the present invention, and in particular, the number of distance measurements and their distance times for each target are determined. In general, the system is specified and attention is focused on measuring the ranging time to the target to which the measurement beam is directed.

  The higher sensitivity of the method according to the invention depends on various factors. First, with a special selection of modulation frequency, the excitation signal is transmitted and received, and its signal waveform is scanned and estimated. The signal waveform may be a series of Dirac pulses as in a phase meter, for example, or a sine wave excitation signal. Second, in the method according to the invention, the total signal information is evaluated to determine the distance. This is different from the use of the phase difference in the phase difference method, and is also different from the distance measurement time in the time-of-flight method. The method according to the invention takes into account the measurement data obtained in all orders in its estimation. For example, all measurements and model information are combined and incorporated into a cost function. Thus, phase measurement is not performed, but not only signal waveforms in a certain time domain or frequency domain, but also signal amplification and noise are measured and incorporated into the estimation. The evaluation of the signal is preferably performed by a cost function based on the maximum likelihood method (optimum estimation). Unlike modern phase meters, the modulation frequency of the excitation signal in a special way, as a function of the number of targets and the spacing between them, by means of a flexible switchable frequency synthesizer. It can be changed or sorted. The system analysis can be performed with high accuracy using the measurement data set in the optimum state. For example, interference due to reflections between multiple targets and telemetry device can be reduced, and interference signal overlap for multiple targets can be bypassed.

  A feature of the system according to the invention is that it is based on a signal with a significantly higher modulation frequency than in a conventional phase meter. The generation of multiple modulation frequencies is due to other recent "frequency hopping devices" such as, for example, DDS synthesizers (direct digital synthesizers) or fractional N synthesizers. According to the present invention, the signal is generated by, for example, direct synthesis, and the signal waveform stored in the internal memory is periodically sent to the digital-to-analog converter in a repeated order and output (arbitrary signal generation). vessel).

  The evaluation is performed separately at each modulation frequency or integrated at a plurality of modulation frequencies. Optionally, another evaluation is suitably performed on a well received signal, for example as a sub-optimal estimate. All signal data is incorporated into a common model and used for parameter evaluation, and particularly with respect to distance measurement time, for example, an optimal estimation method.

  Preferably, only high modulation frequencies in the range of MHz to GHz are transmitted and the system selects a rigid target ranging time and does not react to soft objects such as rain, fog, snow and the like. Another advantage of using a high frequency is that the measurement distance accuracy is further improved. In the case of a special high frequency, that frequency contributes to the final parameter determination. This is different from the conventional phase meter. The advantage of this system is also over a distance meter, which uses a statistical average of 1000 times the number of pulses and has a small pulse repetition rate, resulting in low measurement accuracy.

  Selecting one or more sets of all modulation frequency groups affects the quality of the analysis results of the system. For example, reliable distance measurements can be achieved by optimally selecting the frequency, especially when the target capacity is lower, especially in the case of long target distances. Selecting one or more sets of all signals determines the maximum range that is specially analyzed. All frequency groups are flexibly processed and used for measurement tasks, for example using a DDS synthesizer, the interference effects due to reflections between the telemetry device and multiple targets can be an undesirable signal for multiple targets. Removed with superposition effect.

 The strength of the digital composite signal is influenced by the concept of including flexible frequencies, and thus the optimal use of the entire frequency group for a distance measurement system including the device and measurement distance.

  With the distance measuring method or device according to the invention, it is possible to measure a staggered target, for example as measured via a window frame, unlike a phase meter. The telemetry device can simultaneously measure the distances of multiple targets in the light beam. The concept of optimum frequency is in this case a different concept from that of a single target.

  The distance measuring method according to the present invention can cope with a plurality of targets. In addition, the distance of the internal reference optical path can be measured. The internal reference optical path is the first target. Still other target distances are measured against this reference target. The distance measurement is thus free from temperature changes and further dispersion effects. As a result, the ability to cope with multiple targets is also effective for simultaneous calibration of the internal reference optical path, and the cost previously required by the device for selective switching to the reference distance or for the second reference receiver, Excluded.

  A computing system constructed in accordance with the present invention includes a telemetry unit, an associated target, and a distance to the target. This system is understood from the background of communication technology and is a linear transmission system, the operation of which is understood by the specification of the so-called pulse response h (t).

  For example, when the system is excited by a Dirac pulse, the system responds. The Fourier transform of the pulse response exhibits a transfer function H (ω) or a complex frequency response that represents the system in frequency space or frequency range or frequency domain.

  Since the system is generally excited by a causal signal, it is possible to use a general Laplace transform that is more stable in terms of convergence rather than a Fourier transform.

However, in the case of periodic excitation signals, Fourier transform (FT) is generally considered sufficient. The generally complex transfer function H (ω) of the system is defined as:

The transfer function constituting the system is the ratio between each Fourier transformed signal y (t) and the Fourier transformed excitation signal s (t).
FT: y (t) → Y (ω)
FT: s (t) → S (ω)

The complex frequency response of the system analyzer is given by

ω is an angle of frequency, i is an imaginary unit, and is linked to frequency f as ω = 2 · π · f. Further, d is the number of targets to which the beam is directed, ρ _k is the reflectance, and t _k is the signal ranging time proportional to the distance. The measurement distance is calculated by the formula D _k = c / (2 · t _k ), where c is the speed of light.

  The frequency is amplified, attenuated, and phase shifted by the system. The transfer function consists of two terms whose physical effects are basically different, and is the rational ratio and the sum obtained from the exponential function of the frequency angle as a linear parameter.

  The first term (ratio) shows a so-called dispersion effect and is caused by a laser diode, a receiver diode, a filter, and the like. These change the amplitude and phase from the input to the output of the system.

  The second term consists of the sum of the exponential function and indicates the obtained delay time or ranging time between the telemetry unit and each target. The calculation of the delay time corresponds to the measured distance of each target.

  In order to be able to measure the ranging or lag time of the system with high accuracy, the first term expressed as a ratio needs to be removed by calculation or calibrated to the system.

  This can be ensured, for example, by manufacturing system calibration during production or in the next cycle prior to delivery. In the case of difficult-to-evaluate aging that increases the delay in distance measurement time due to frequency, periodic system calibration in the field or calibration during or immediately before the actual distance measurement is advantageous.

  The calibration of the system is preferably performed at a time related to the distance measurement. For this purpose, the measuring light is passed over an internal optical path of known length. As a result, the first term data of the transfer function is determined at the excitation frequency used.

  The actual distance measurement is performed sequentially or simultaneously. Measurement light is sent to an external target. The external ranging of the system is preferably carried out at the same frequency as in the internal optical path, i.e. obtaining a transfer function. On the other hand, in the prior art, only complex solutions are known, i.e. a switchable reference distance or a duplex design of the transceiver. For example, EP0738899 discloses a variable reference distance, EP0932835 describes the use of two receivers and DE400002356 discloses the use of two switchable transmitters.

  In accordance with the present invention, the measurement is performed by the internal optical path and by the external optical path. This is because this method estimates multiple targets with high accuracy, and the internal reference distance is measured as the first of the multiple targets. Thus, the system does not need to provide a double element and a switchable reference distance, unlike the prior art measures.

  In accordance with the present invention, the technical operation for calibrating this system is that when a certain amount of frequency is selected (regular or irregular frequency selected), in particular the second external measurement across the internal optical path. A transfer function H (ω) is set along the optical path.

For calibration of this system, equation (1) is well represented in polar coordinates or exponential representation.

Due to the calibration of the system, the amplitude H (ω) and eigenvalue t _disp (ω) of the system are determined at the frequency used for the measurement signal. These frequencies are used for actual distance measurements to the target.

  Therefore, among other things, at the measurement frequency, amplitude or attenuation, correction of each delay time is taken into account. These undesirable effects are included in the first two terms of the transfer function.

The calculation of the transfer function is performed by, for example, a separation Fourier transform (DFT). The received signal is scanned within that time by an analog-to-digital converter (ADC), after which the frequency contained in the measured signal and the composite amplitude Y (ω) are calculated by DFT to determine the amplitude of the system. H (ω) and eigenvalue t _disp (ω) are obtained.

  For internal and external measurement paths, the transfer function can be corrected by comparing the amplitude, phase and noise related to the frequency, and only the term of the delay time k with respect to H (ω) or H (f). Is unknown in its exponential formula.

Therefore, as a transfer function of calibration data,

For multiple goals d,

The ranging time calibrated for the measured target is expressed by t _k for simplicity.

  The system calibration is performed directly in that time domain. With respect to the transfer function H (f), the ranging time of the system is determined by referring to the internal optical path in response to various excitation signals.

  The system is calibrated on the principle of maximum likelihood estimation, and all measured system response values are integrated into a single cost function to estimate calibrated distance measurement data for the target.

Knowing the full continuous spectrum, the response pulse of the system can be calculated by inverse Fourier transform (IFT).

If H (f) corresponds to Equation 3 and is known at all frequencies, it can be integrated, and the response pulse is
If you have one goal,

For multiple targets d,

It is clear that the response pulse contains the total distance data t _k of the target d in the measurement beam.

  Even if direct measurement is performed at the modulation frequency, Equations 3 and 4 are valid if heterodyne or homodyne measurement is performed. The high frequency received signal is mixed with the high frequency mixer signal to become a low frequency electronic signal. By estimating the low frequency signal, the amplitude and phase of the actual high frequency received signal can be determined.

  In the embodiment of the telemetry device according to the present invention, not all of the complex spectrum H (f) of the system is measured, and the measured or transmitted signal is transmitted to the system for only a part of the total system frequency. Excited, usually only a group of measurement and transmission frequencies. The spectrum H (f) is therefore not part of all frequencies but part of it.

  Furthermore, it is not possible directly by IFT to reconstruct the pulse response h (t) as a time signal.

The parameter calculation of the distance measurement time t _k in Equations 3 and 4 is theoretically problematic.

  Various estimation methods are suitable for calculating distance measurement time and distance. The selection of the optimal method in each system depends on the characteristics of the state in the system. For example, the characteristics of the system are the number of targets, the distance to the target, the reflectance of the target, the amplitude of the signal, the magnitude of the noise level, and the like.

  To obtain a part of the distance data, the entire signal shape y (t) or just a part of the signal shape can be used, for example the following quantity: That is, in the maximum value of the signal shape y (t) and the curve y (t), it is the first harmonic function or region, or the signal pulse region of 1/2 maximum amplitude value. In statistical estimation, the RMS noise of the signal shape y (t) is interpreted as part of the signal shape.

  The main part of the distance data is configured as a signal shape that is a function of time. For example, the multiple system responses y (t) are known with respect to the excitation signal s (t), which is a function of time, and in particular with respect to multiple targets, each reflected pulse as a time function in the system is alternating. . In the instantaneous analysis, the signal pulse centroid position as a time function is interpreted as a feature of the signal shape as a time function.

  In the following, some estimation examples in the time or frequency domain are described as non-limiting examples.

  The first method of distance calculation is estimation in the time domain. For example, the distance measurement time of a periodic pulse in a short time is sequentially measured for each pulse, and the distance is measured with high accuracy by a unique method.

  In calculating the distance in a certain time range, it is important to optimally select the pulse repetition peripheral number. These are selected so that signals reflected from multiple targets arrive at the receiver at different times. As a result, there is no hassle of overlapping signal pulses, and each signal pulse is unified with each target.

According to the present invention, an optimum frequency is selected using a frequency synthesizer. An example of the estimation method is shown in FIG. 5a. Each excitation signal s (t) results in a response signal y (t). A signal response h (t) calibrated by the internal optical path is obtained from the signal. For all excitation signals s (t), these calibrated signal responses h (t) are shifted in time with respect to each other to calculate the relationship shift time Δt _jk by, for example, cross-correlation calculation or centroid calculation. can do. These shift times Δt _jk provide information based on the number of pulses carried the measurement distance (a unique method).

In a further step, it is possible to construct a time signal z (t) formed from the sum of the time-shifted signal responses h _k (t−Δt _jk ) of the total excitation signal s _k (t). For example, the distance measurement time tn is finally calculated from z (t) by cross correlation calculation or center of gravity calculation.

Yet another method is a non-linear balance operation between the special model of the transfer function H (f) according to Equation 3 and the measurement point H (f _k ) at the analytical modulation frequency.

  Another method of distance estimation is based on the principle of maximum likelihood estimation. The measured spectral data is input to the cost function, and the distance of the target d is obtained by the maximum or minimum value of the entire function.

  In one special case, the maximum likelihood estimator is a simple one-dimensional cost function with an overall maximum. Other methods are provided in that special case where the composite spectral separation measurement data is properly selected and accurate and reliable distance estimation is possible as well. For example, the inverse Fourier transform of the separation and selection frequency can be interpreted as a maximum likelihood approximation.

For a single target, the following formula applies:

The complex function z (t) is obtained directly from all number N of measured complex amplitudes H (f _k ), corresponding to the time signal, of the inter-separation number spectrum. The function contains all the data corrected by the system analysis. The overall maximum value of the time function Re (z (t)) corresponds to the distance measurement time t1.

  Inverse Fourier transform (IFT) can be used in the case of multiple targets. However, additional conditions are incorporated in the selection of the composite amplitude obtained from the system analysis of the separation frequency. Due to the irregularly selected part of the transfer function, a one-parameter time function having a maximum value is obtained with respect to the ranging time of the target d.

ウインドウ関数Ｗ（ｆ）は、複数目標の場合の距離測定の精度を著しく向上させる。 In the case of multiple targets, the IFT is expanded by a window function W (f) known from the theory of Fourier transform. For example, a Hanning window or a Blackman window, and the following formula is applied.

The window function W (f) significantly improves the accuracy of distance measurement in the case of multiple targets.

  Examples of frequency concepts suitable for multiple targets are given below.

  A frequency concept that is optimal for multiple targets and is in the form of a frequency set is formed by equally spaced excitation frequencies. Such a concept has, for example, frequencies of 400 MHz, 410 MHz, 420 MHz,.

  The magnitude of the time signal z (t) generated by the IFT can be calculated appropriately. A typical shape of a time signal obtained from equally spaced excitation frequencies is illustrated in FIG. The distance measurement time is obtained from the calculated pulse time signal z (t). The occurrence of multiple pulses indicates that there are multiple targets. Due to the measured separation frequency, the calculated time signal is periodic in time. The calculated periodicity of the time function limits the maximum range. By appropriately selecting a set of equally spaced frequencies, the maximum range is extended to 500 m without reducing measurement accuracy.

  In order to reduce the number of excitation frequencies required for system analysis, the frequency is divided into a plurality of frequencies at equal intervals. In other words, in the first analysis step, it means that a uniform frequency with a fine frequency interval is emitted. The time signal z (t) or z (t) is calculated by IFT, and an approximate distance is obtained. In the example shown in FIG. 14, they are 100 MHz, 100.5 MHz, 101 MHz, 101.5 MHz,.

  In the second analysis step, another set of equally spaced frequencies with coarser frequency intervals is fired and the corresponding time signal z (t) is again calculated by IFT. As a result, the distance is accurately calculated. An example is shown in FIG. 14, and they are 100 MHz, 107.5 MHz, 115 MHz,. If the measurement distance accuracy is inadequate, the system analysis will improve accuracy using evenly spaced perimeters at finer intervals.

  Instead of the time signal z (t) as a cost function, the power signal [z (t)] · z (t) generated by the weighted IFT may be used to calculate the distance. [z (t)] represents the complex conjugate number z (t).

  The system is excited by a periodic transmission signal as input. In the simplest case, this is a harmonic sinusoidal vibration. Preferably, however, short duration pulses, for example in the form of rectangles, triangles, Dirac pulses, or other shapes, are made periodically. The frequency spectrum of the transmitted signal is therefore discrete, and in addition to the fundamental harmonic frequency, a corresponding higher harmonic frequency is simultaneously created in the spectrum according to the pulse shape.

  For system analysis, multiple periodic transmission signals with different frequencies are used. These are in turn used for system inputs and the corresponding output signals are measured. When all periodic signals are measured, the system measurement (system analysis) is completed. In addition to the fundamental harmonic frequency of the periodic signal response, a higher harmonic spectral component of that response is measured in that spectral range.

  In an embodiment of the invention, a set of excitation frequencies can be made, for example by means of a DDS synthesizer (direct digital synthesizer). A compact single chip module is very accurate and can actually generate any number of perimeters. The switching time for changing the frequency is shorter than milliseconds, and is negligibly short compared with the necessary measurement time for system analysis. The switching is controlled by a microprocessor via a data bus, for example. The synchronous timing frequency of the DDS module is generated by a ppm-based master oscillator. This frequency can in this case be the basis for calibration of all excitation frequencies, ensuring distance analysis in ppm.

  In addition to DDS frequency synthesizers, other modern "frequency popping devices", fractional N synthesizers are known. Due to the rapid gradual frequency switching, these modules are suitable as generators of the required modulation frequency.

  The advantage is to determine the signal strength (amplitude) of the emitted excitation frequency. This is because it is used to calculate the transmission complex function H (t) by knowing the amplitudes of both the transmission signal and the reception signal.

  The format and selection of each optimum periodic excitation depends on system characteristics such as the number of targets, the target distance, and the signal to noise ratio, as well as the distance calculation method. In view of these actual features, the excitation spectrum of the system analysis can be optimally selected and flexibly formed in the field using a DDS synthesizer and additional elements.

  When there is one target, for example, the repetition frequency of the periodic transmission signal having logarithmically spaced steps is selected. The cost function s (t) is calculated by inverse Fourier transform, and as shown in FIG. 12, an overall maximum value suitable for an estimation method strong against noise is obtained.

  In the case of a target plate where multiple reflections between the target point and the telemeter device occur, the repetition frequency of the transmission pulses is preferably the main number and is used in an adjusted manner. The cost function s (t) is calculated by inverse Fourier transform, and an overall maximum value suitable for the distance estimation method obtained by the target plate is obtained.

  In a measurement state where there are multiple targets in the measurement beam, for example, a periodic transmission signal with equally spaced frequency steps is used for system analysis.

  For example, in order to be able to measure a long distance range of 500 m with high accuracy (approximately mm), multiple sets of excitation frequencies with equally spaced steps can be used as described above. Basically, two sets of excitation signals with different spacings between repetition frequencies are sufficient, as shown in FIG.

  In summary, the following three estimation methods basically achieve that purpose of system analysis.

  1. One method is the estimation of system data over a certain time range. By measuring the associated ranging time of the signal response in all pulse sequences that are shifted with respect to each other in time, the number of pulses that are sent simultaneously along the transmission distance (unique) is determined. The target distance to be obtained is finally obtained by combining the distance measurement time value between the latest transmitted and received pulses and the number of pulses between the transmitting and receiving units.

  2. Another method is an estimate over the frequency range. By applying DET or FFT to the measured periodic time signal, the parameters of the transfer function H (f) are calculated at the excitation frequency (including higher harmonic frequencies). When the transfer function H (f) is measured for a sufficient frequency, the distance is calculated by, for example, a least square method, a cost function based on a maximum likelihood method, or a cost function based on other criteria.

  3. Yet another method is to extend the estimation in the frequency range. When the transfer function H (f) is measured at a sufficient number of frequencies, the time signal z (t) corresponding to the pulse response is reconstructed by applying IFT and the estimation is reapplied in that time range. Is done. The delay time of the system or the distance measurement time for each target is determined by the signal maximum value / minimum value of Re (z (t)).

  On the device side, the received optical signal reflected by the target is preferably detected by an electronic wide band optoelectronic receiver. The excitation signal is a high-frequency signal in the MHz or GHz range. To avoid scanning signals at an analog-to-digital converter (ADC), in one embodiment, for example, the received signal is sent to an electronic mixer (heterodyne receiver). At the output of the mixer, the time signal converted to low frequency is scanned by the ADC, and the measurement point data is sent to the estimation unit or memory.

  Scanned time signals with different repetition rates are preferably converted by DET to a frequency range, and the result is the composite amplitude of the transfer function H (f) at each frequency. Further measurement points of the transmission complex function H (f) are determined by each periodic transmission signal or excitation signal. When sufficient measurement points of the transmission complex function H (f) are obtained, the distance calculation can be started by one of the methods for calculating the delay time.

  An embodiment according to the present invention, in which the system analysis can be performed without increasing the measurement distance and being affected by rain, snowfall, and fog when the number of targets is one, is as follows. The excitation frequency for system analysis is generated by the DDS synthesizer, and the amplitude of the excitation frequency is determined. The amplitude of the excitation frequency is calibrated once at the factory.

  Signal reception is designed to be heterodyne with an electronic mixer and PLL signal, and signal sensing is performed by pulse-synchronized digitization using an ADC. As a replacement example, scanning the signal directly in the high frequency range can be implemented instead of the heterodyne reception method.

  The first step of estimating the digitized received signal is performed by DFT conversion in the processing unit. Calculation of the time signal equivalent to the pulse back feather etc. is performed by the IFT method.

  A time signal equivalent to the pulse response is calculated by the IFT method. Rain, fog, or snowfall reflects a portion of the optical transmission signal. However, since the signal component is dissipated and integrated over the entire measurement distance, the delay time independent of the frequency is not superimposed on the pulse response, but the distance measurement time related to the frequency is superimposed ( Dissipated). From theoretical studies and experiments, the interference effects of scattering on the system ranging time disappear as soon as the excitation frequency exceeds 10 MHz. Since the influence of rain and fog on the signal amplitude appears at a low frequency, the frequency of about 1 to 5 MHz may be deleted. Therefore, if only modulation frequencies greater than about 10 MHz are used for system analysis, the effects of falling particles in the air are negligible in actual target distance measurements.

  The use of a large number of modulation frequencies according to the DDS technique is more advantageous because it allows more data. For example, if a light measurement beam happens to be interrupted by a person during system analysis, a discontinuity will occur in the transfer function H (f), but the effect is easily detected because of the large number of modulation frequencies, It is ignored for further signal estimation. The remaining spectral portion of H (f) is sufficient for distance measurement and has no effect on accuracy.

  Another embodiment according to the invention relating to a system analysis device in the case of multiple goals is provided, for example the following strategy.

  For the system analysis, preferably the flexible generation of the number of excitation frequencies is performed using a first DDS that generates a very high frequency, in combination with a frequency converter in the downstream circuit. The Its frequency converter ensures high-precision distance measurement. Even without a PLL, it is possible to switch frequencies rapidly in microseconds. The amplitude of the excitation frequency is determined on the transmission side, but it can also be calibrated once at the factory. In the receiving circuit, a rapidly switchable DDS synthesizer mixes the signals for heterodyne or homodyne reception. Frequency tuning is performed sequentially in a frequency range that is greater than the first DDS can accept. Digitization by ADC is used for signal measurement. The estimation of the signal by DFT or IFT is performed in the processing unit, and a time signal is calculated in the same manner as the pulse response.

  The method according to the invention and the devices suitable for carrying out this method are described in more detail below and illustrate the embodiment illustrated in the accompanying drawings by way of example.

  1a and 1b illustrate the principle of a pulse measuring method according to the prior art.

  In FIG. 1 a, the transmitter 1 emits a light pulse 2, which is reflected by the target or counter reflector 3 and then detected by the receiver 4. In general, the transmitter 1 and the receiver 4 are arranged in one unit.

  The distance is calculated from the distance measurement time L. The distance measurement time is the difference between the start time S and the reception time E of the light pulse 2. The determination at the time of reception is performed based on the characteristics of the signal pulse s (t), for example, based on whether or not the signal exceeds a threshold value, or by integrating the pulse curve and calculating the center of gravity.

  2a and 2b are diagrams illustrating the principle of a phase measurement method according to the prior art, in which the distance between the measurement unit and the target is calculated.

  In FIG. 2a, the transmitter 1 'emits a modulated optical signal, which is the light wave 2, to the target, and the optical signal is reflected back to the target and returns to the receiver 4'. Contrary to the distance measurement time method, the time between transmission and reception is not recorded in this case. The phase difference between the input signal and the output signal is recorded. This difference depends on the distance between the measuring device and the target. This distance corresponds to a multiple of the wavelength W of the emitted light pulse 2 'and the remainder R. This residue is a component that remains when the distance is divided by the wavelength W shown in FIG. In order to know the phase shift, the distance between the measurement unit and the target can be obtained by measuring the residual R and grasping the number of the residual R and the wavelength W. In this method, since the number of wavelengths W cannot be obtained directly as an integral component, it is necessary to perform an additional analysis for obtaining this unknown. For example, a plurality of modulation frequencies (2 to 5) are used. For this reason, the absolute phase of the received signal is sequentially calculated with respect to the transmission signal. One target distance is obtained from these multiple measurements.

  A suitable example of a prior art phase meter is shown in FIG. 3 by a block diagram. In the transmitter 1 ', the signal is modulated with respect to the light of the radiation source SQ by the modulator MO. The modulator is controlled by a high frequency oscillator OSCI. After being detected by the optical device of the receiver 4 ', the reflected light is converted into a low frequency signal by the optoelectronic converter OEW. For this purpose, the signal of the superposition oscillator UEO is applied to the optoelectronic converter OEW. A mixing step MS for generating a low-frequency resonance signal from the signal of the high-frequency oscillator is performed by the superposed oscillator UEO. The low frequency signal is converted into a square pulse by the trigger TR. The phase measurement unit PME arranged downstream thereof compares the signal of the high-frequency oscillator OSCI with the low-frequency signal mixed with the received light to calculate the phase difference. The distance is calculated from the phase difference.

  FIG. 4 is a diagram generally showing the principle of the system analysis measurement method according to the present invention, in which a system model of a telemetry device as a linear transmission system is applied to a plurality of targets. The light pulse 2 ″ is emitted by the transmitter 1 ″. The light pulse 2 "is reflected by multiple targets. These targets are here the first target 3a and the second target 3b. The reflected signal is detected by the receiver 4". The whole system has a transmitter 1 ", targets 3a, 3b and a receiver 4" and is understood as a substantially time independent system (LTI system). However, this does not allow the target to move, but allows small movements within the measurement time for system analysis. In order to obtain the distance data, the signal s (t) is applied to the system input SE and the signal amplitude y (t) of the system response, resulting in system data recorded at the system output SA. Here, the system input and output are interfaces to the outside of the LTI system.

FIG. 5a is a diagram for explaining the principle of an embodiment of the system analysis measurement method according to the present invention in a time range. The LTI system is repeatedly excited by a pulsed periodic signal. The pulse signal, in any case, consists of a plurality of separation (different) frequencies. For each excitation pulse s (t), the signal amplitude or signal waveform y (t) of the system response 5 is recorded by the receiver. The pulse repetition frequency is changed from f _j to f _k to obtain the corresponding signal response time shift Δt _jk . This time shift Δt _jk provides information on the number of pulses simultaneously over the transmission distance and provides an approximate value for the survey distance. The accurate distance result is finally obtained by measuring the distance measurement time difference between the transmitted and received signal pulses. For this purpose, a time signal z (t) 6 is constructed from all the time shift response signals h _k (t−Δt _jk ). From z (t), the distance measurement time t _n is obtained by a probability average.

FIG. 5b illustrates the principle of a further embodiment of the system analysis measurement method according to the invention. The LTI system is repeatedly excited by signals each consisting of multiple separation frequencies. At each excitation, the signal amplitude or signal waveform y (t) of the system response 5 ′ registered in the receiver is recorded and a separate Fourier transform (DFT) is applied. A transmission complex function at each excitation frequency of the transmission signal is obtained from the DFT. In each case, the amplitude S _j and the phase shift ψ _j are calculated from the real part and the imaginary part at various frequencies of the spectrum. Again, a time signal z (t) 6 ′ is obtained by reconstruction from the spectral set of the total system response for the various excitations by inverse separation Fourier transform (DFT). The time signal z (t) 6 'is equivalent to the distance signal z (D), where the time parameter t is multiplied by half of the speed of light c. In this example, the ranging times t ₁ , t ₂ distinguish between the two targets, and their distance is obtained from the curve of the reconstructed time signal 6 ′.

Figures 6a and 6b illustrate the input and output parameters for the system model of the method according to the invention. FIG. 6a shows a triangular pulse, which is a periodic repetition of the MHz range that excites the LTI system and applies to the system input. The maximum value of the signal amplitude z (t) corresponds to the time t = 0. FIG. 6b illustrates the system response y (t), which is detected by the receiver and provided as the system output. In the case of the two goals described here, this response forms two triangular received signal amplitudes y (t), the peaks of which are received at times t ₁ and t ₂ .

FIG. 7 shows the system model of the method according to the present invention, integrating the partial system d to provide the LTI system 7, each partial system corresponding to one target. With respect to a system having a ranging time or delay time tn, the superposition principle, the amplification principle and the exchange principle are applied to the linear system. Thus, the systems are sequentially exchanged with respect to delay times, and sub-systems of the LTI system can be applied to other processes and other integrations. The signal y (t) at the system output SA is a linear and interchangeable superposition of the system responses y ₁ (t−t ₁ ) to y _d (t−t _d ). The system response corresponds to a partial system with each excitation s ₁ (t) -s _d (t) resulting from application of signal s (t) at system input SE. The system model shown in FIG.

  FIG. 8 shows a suitable transmission signal for system analysis, for example, a sine wave (top), a series of needle or Dirac pulses (middle), and a rectangular pulse (bottom).

  FIG. 9 is an example of an appropriate spectral distribution of the total amount of transmission signals. Appropriate spectral distribution of the total amount of all transmitted signals (sum of all excitation signal spectra) is important for system analysis. For a transmission signal (single period), a plurality of frequencies are basically created (Fourier series). In accordance with the present invention, all simultaneously emitted frequencies are measured, recorded and estimated.

  In order to complete the system analysis, it is important to specify a spectral range as the sum of all the frequencies, with a plurality of transmission signals having different periods being sequentially fired. This spectral range designation consists of all transmission and reception frequencies, but may be different. The frequency may be, for example, at equally spaced or logarithmically spaced positions. Furthermore, the frequency interval can be selected by the basic number or the Hibonacci number. In FIG. 9, the frequency distribution shown in the upper stage corresponds to equally spaced positions, and the frequency interval shown in the middle stage is selected by selecting the basic number. On the other hand, the lower distribution is logarithmically spaced. In the upper and lower distributions, all measured signal quantities are clearly spectrally displayed on the receiver side (low pulse), and the construction of the model and the scanning are performed.

  FIG. 10 shows another example of an appropriate spectral distribution of the total amount of all transmitted signals, showing the separation frequency with limited width. The spectral distribution of all excitation signals is equally spaced (upper) or logarithmically spaced (lower).

  FIG. 11 shows another example of a suitable spectral distribution of the total amount of all transmitted signals, in the form of two sets of separation frequencies, each of which is a different equidistant arrangement. The distance between the two sets is preferably different.

FIG. 12 shows, as an example, a time signal or a distance signal reconstructed by IFT (Inverse Fourier Transform) of system analysis when the spectrum is logarithmically spaced. The time signal z (t) is calculated as a cost function by system analysis with logarithmically spaced excitation frequencies. Optimal estimation of ranging time is obtained by data estimation, which includes data for all parts of measurements performed in parallel and in series. In the case of one target, a time signal is calculated by IFT from the transfer function H (f) using an optimal estimation method based on the maximum likelihood method. The required distance measurement time t _n or the target distance D _n corresponds to the maximum signal peak. The illustrated time signal is an IFT of the transfer function H (f _k ) at the frequency point f _k .

FIG. 13 illustrates, as an example, an envelope of a time signal as an IFT for system analysis when the spectrum is logarithmically spaced. The target distance Dn is calculated from the reconstructed time signal | z (t) |. The time signal is calculated as a cost function by system analysis with equidistant excitation frequencies. The time signal is produced by an IFT of the transmission complex function H (f _k ) with respect to the measured frequency point f _k . The required ranging time corresponds to the highest signal peak. The distance measurement time and the distance measurement distance correspond to each other. This is because D = c / (2.t).

FIG. 14 illustrates an example of a two time signal that is an IFT of two spectrally spaced frequency sets. The distance D _n is calculated from the time signal z (t) as a cost function by system analysis with two different sets of equally spaced excitation frequencies. The first time signal z1 (t) indicated by the dotted line is determined by the IFT of the transmission complex function obtained from the measurement data of the first frequency set. The second time signal z2 (t) indicated by the solid line is obtained by the IFT of the transmission complex transfer function determined from the second set of frequencies. The rough estimation of the required distance measurement time corresponds to the maximum signal peak of the first time signal. The exact estimated value of the ranging time to be obtained corresponds to the maximum signal peak of the second time signal. The maximum value of the second time signal coincides with the first time signal.

  FIG. 15 illustrates a power signal that is an IFT of two equally spaced frequency sets for two differently reflecting targets. A preferred cost function | P (t) | for multiple targets is shown. The cost function is the envelope of the power signal P (t) of z (t) related to time when two targets are measured. The first power signal P1 (t) (indicated by a dotted line) is generated by an IFT of a complex transfer function obtained from the measurement data of the first frequency set. The second power signal P2 (t) (shown as a solid line) is generated from the IFT of the transmission complex function obtained from the second set of frequencies. The rough estimation method of the distance measurement time to be obtained corresponds to the maximum signal peak of the first power signal | P1 (t) |. The accurate estimation method of the required distance measurement time corresponds to the maximum signal peak of the second power signal | P2 (t) |. The maximum value of the second power signal coincides with the first power signal.

  A simple example of optoelectronic system analysis as a device according to the present invention is shown in block diagram in FIG. 16 and has a heterodyne mixer. DDS (direct digital synthesizer) technology is used and in this model all arbitrary harmonic frequencies and arbitrary signal shapes are programmable. The synthesizer is switched in milliseconds by the microprocessor. Therefore, in a short time, it is possible to scan all the frequencies necessary for system analysis and know the real and imaginary parts of the transfer function. A phase locked loop PLL, together with a voltage controlled oscillator VCO, can create a phase stable mixing frequency for a heterodyne receiver. In the case of direct scanning of the system response or reception of a homodyne signal, the PLL is omitted. The oscillated signal is converted to a very high frequency by the frequency converter FC. After the amplifier circuit A, the received signal is converted into a low frequency time signal by a product mixer MIX, sent to a low frequency filter LF, and digitized by an analog-to-digital converter ADC. The signal data is accumulated in the processing unit PU and stored in the memory M if necessary. The frequency stable master oscillator OSCI is used as a time reference.

  FIG. 17 shows a block diagram for another embodiment of a device according to the invention, comprising a heterodyne mixer, increasing the flexibility in frequency selection. The generation of the excitation frequency for system analysis is performed by a first DDS synthesizer connected to a frequency converter that generates a very high frequency. In that arrangement, a phase-locked loop PLL is provided, which has various advantages, for example, allowing rapid frequency switching in microseconds, or without a narrow lock range of the PLL, the frequency range of the DDS. Are all used. The second DDS synthesizer can be switched quickly and generates a mixed signal for heterodyne reception. The frequency converter FC converts the excitation mixed signal into a necessary frequency band. The frequency stable master oscillator OSCI is used as a time reference. The other modules are a heterodyne mixer MIX, an analog-digital converter ADC for signal scanning, a data storage memory M, and a processing unit PU as a control / estimation unit.

  FIG. 18 illustrates a theodolite telescope as an example of a geometer according to the present invention and comprises a device according to the present invention. The light from the radiation source 8 disposed on the support member 9 common to the estimation electronic unit 10 is radiated to the first target 3 a via the switchable polarization element 11, the reflective polarization means 12, and the lens 13. The target 3a represents the target and is not limited to a single target. After being reflected by the target 3a, the light is collected by the lens 13 and sent to the receiver 15 via the dichroic mirror element 14 and the reflective polarization means 12 for signal processing. The signal from the receiver 15 is processed by the estimation electronics 10 and the distance is stored. By means of the switchable polarization element 11, a part of the light emitted from the radiation source 8 is sent directly to the receiver 15 and an internal reference system suitable for system calibration is used. The lens 13 may be used as a transmission / reception lens, and two lenses may be arranged on two axes.

  In addition to the signal processing means, the theodolite telescope comprises a visual light system to provide light reflected back from the first target 3a that can be used by an observer (human). The focus member 16 and the eyepiece member 17 have different elements, for example, inverted prisms, which are used for this purpose.

  FIG. 19 illustrates a theodolite telescope having a device according to the invention, with an additional device for autofocus. This embodiment is designed in principle in the same manner as in FIG. 18, and includes an adjusting member 18 that is controlled by the estimation electronic unit 10 and automatically adjusts the focusing member 16.

  Another embodiment of the theodolite telescope is illustrated in FIG. 20 and is another embodiment of a beam path having a device according to the present invention. The light is emitted from the radiation source 8 disposed on the common support member 9 together with the estimation electronic unit 10 and reaches the reflection polarization means 12. The reflective polarization means 12 deflects a portion of the light and sends it directly via the beam splitter 19 to both the receiver 15 and the lens 13 and thus at least one target 3a. After reflection, the light is again collected by the lens 13 and sent to the receiver 15 via the dichroic mirror element 14 and the beam splitter 19 for signal processing. The signal of the receiver 15 is processed by the estimation electronic unit 10 to obtain distance data. The internal reference distance is provided by the beam splitter 19. In this case, the system calibration is performed simultaneously with the distance measurement of the external target.

  FIG. 21 illustrates schematically a scanner having a device according to the invention. In order to store the three-dimensional image, the light from the radiation source 8 arranged in the housing with the estimation electronic unit 10 ′ in the common support member 9 ′ is reflected polarization means combined with the beam splitter 19 ′ and the lens 13 ′. 12 and 12 'to the target to be recorded. In this figure, this target has various surface structures and is represented by the first target 3a.

  After reflection, the light is collected by the lens 13 'and sent to the receiver 15 via the dichroic mirror element 14'. In special measurement situations, part of the ranging light is sent to the image sensor 20 via the dichroic mirror element 14 '. The signal of the receiver 15 is processed by the estimation electronic unit 10 'to obtain distance data. A focusing member 16 is disposed between the dichroic mirror element 14 ′ and the image sensor, and an adjusting element is provided in the same manner as in FIG. 19 and is automatically adjusted. The measurement content detected by the image sensor is thus sharply focused.

  Due to the beam splitter 19 ', a part of the light emitted from the radiation source 8 is sent directly to the receiver 15 to obtain an appropriate internal reference distance for system calibration in this embodiment as well.

  Control and orientation of the scanning light beam is accomplished in a known manner that pivots the entire device to change the firing direction. In this example, the movement of the overall device is clearly illustrated, for example with an internal adjustment element or a beam correction light element. In this example, the entire device is mounted to pivot about a horizontal axis HA and a vertical axis VA, and the scanning capability for the entire measurement area is expanded by a combination of horizontal and vertical pivoting operations.

  FIG. 22 illustrates a two-axis telemetry apparatus having a device according to the present invention. The internal optical path can be switched freely for simultaneous calibration. The light from the radiation source 8 arranged on the common support member 9 ″ together with the estimation electronics 10 ″ is emitted as a transmission beam and is sent to the target 3 a through the light transmission device 22 through the exit window 21. After reflection, this light is collected by the lens 13 "and sent to the receiver 15 for signal processing. The signal of the receiver 15 is processed by the estimation electronics 10" to obtain distance data. It is done. A part of the transmission beam is reflected by the exit window 21 and hits the receiver 15 arranged in two axes. The position and intensity of the reflection is determined by a suitable surface treatment, such as the top coating of the exit window 21 or the application of the reflective element 23.

1a and 1b are diagrams illustrating the principle of a pulse measuring method according to the prior art. 2a and 2b are diagrams illustrating the principle of a phase measurement method according to the prior art. It is a block diagram of the phase meter by a prior art. It is a schematic diagram which shows the principle of the system analysis measurement method by this invention, and has a some target object. 5a and 5b are diagrams illustrating the principle of an example of the system analysis measurement method according to the present invention. Figures 6a and 6b illustrate the input and output quantities for the system of the method according to the invention. Fig. 4 shows a system model of the method according to the invention, combined with various partial systems. An example of an appropriate transmission signal for system analysis is shown. The example of suitable spectrum distribution of the whole quantity of all the transmission signals is shown. The separation frequency which restricted the band pass which is another example of the spectrum distribution of the whole quantity of all the transmission signals is shown. It is another example of the spectral distribution of the total amount of all transmitted signals, showing two sets of separation frequencies, each set being at a different equidistant position. It illustrates a time signal and is the real part of an IFT (Inverse Fourier Transform) of logarithmic equidistant system analysis of the spectrum. An example of a time signal shows the amplitude of an IFT (envelope) for equidistant system analysis of the spectrum. Two time signals are illustrated, showing the IFT amplitude of a set of equally spaced frequencies of two spectra. Illustrating a power signal, showing an IFT of two equally spaced frequency sets of two spectra, showing two different reflection targets. 1 shows a block diagram for a device according to the invention, having a heterodyne mixer. A block diagram for a device according to the invention is shown, having a heterodyne mixer, improving the flexibility of frequency selection. 1 is an illustration of a theodolite telescope comprising a device according to the present invention, and is an example of a geometer according to the present invention. FIG. 2 is an illustration of a theodolite telescope with a device according to the invention, additionally using automatic focus control. 1 is an illustration of a theodolite telescope comprising a device according to the invention, having a switchable internal optical path for simultaneous calibration. Fig. 2 is an illustration of a scanner according to the invention, comprising a device according to the invention. FIG. 2 is an illustration of a biaxial telescope with a device according to the invention, having a switchable internal optical path for simultaneous calibration.

Explanation of symbols

1, 1 ', 1 "Transmitter 2, 2', 2" Light pulse 3 Target (reflector)
3a, 3b Target 4, 4'4 "Receiver 5, 5 'System response 6, 6' Time signal 7 LTI system 8 Radiation source 9, 9 ', 9" Support member 10, 10', 10 "Estimation electronics 11 Polarizing element 12, 12 'Reflective polarizing means 13, 13', 13 "Lens 14, 14 'Dichroic mirror element 15 Receiver 16 Focus member 17 Eyepiece member 19, 19' Beam splitter 20 Image sensor 21 Exit window 22 Optical transmission System 23 reflective element

Claims (50)

A method for obtaining geodetic distance data,
Comprising a signal generator for generating at least two modulation frequencies in the MHz to GHz range;
A transmission system (7),
The transmission system comprises a receiver (4, 4 ', 4 ") having a transmission system input, an optical radiation source (8), a single or a plurality of targets (3, 3a, 3b) and a transmission system output. )
The estimation electronics (10, 10 ', 10 ")
The method
Applying at least one excitation signal having at least two modulation frequencies from the signal generator to the transmission system input to excite the transmission system (7);
Scanning and recording at least one system response (5, 5 ') at the transmission system output using an analog to digital converter;
Obtaining at least one distance data from the signal waveform of the at least one system response (5, 5 ') by the estimation electronics (10, 10', 10 "),
When obtaining the at least one distance data,
At least part of the signal waveform of the at least one system response (5, 5 ');
and,
From the temporal composition of the signal waveform of the at least one system response (5, 5 '),
Obtaining the distance data;
Further, when obtaining the at least one distance data, the at least one distance data is determined according to a transfer function of the transmission system evaluated from the at least one transmission system response.
The method as described above.   The method of claim 1, wherein the at least two modulation frequencies are a group of discrete modulation frequencies.   The method of claim 1, wherein the system is a transmission system.   The method of claim 1, wherein the distance data is determined according to the transmission system model.   The method of claim 4, wherein the transmission system model is a linear time invariant system (LTI).   The method of claim 1, wherein the distance is determined according to a transfer function (H (w)) of the transmission system evaluated from the at least one system response in a frequency domain. The transmission system model has at least one parameter that represents a deviation in system response to the excitation signal that is a function of time, i.e., a delay time of the transmission system;
The distance data is determined according to the delay time as a transition time of the signal going back to the target.
The method of claim 1.   The method of claim 1, wherein the transmission system response comprises a change in amplitude and phase from an input to an output of the transmission system. A transmission system specification is performed to determine the transition time to the target where the light emission is directed, or
The method of claim 1, wherein the linear time-invariant (LTI) transmission system is specified at at least two modulation frequencies.   The method according to claim 9, wherein the transmission system specification is performed in a frequency domain. The method of claim 1, wherein
The at least one target (3, 3a, 3b) scatters a portion of the light radiation;
Method wherein the receiver (4, 4, 4) converts the scattered light radiation into the signal at the receiver output.   The method of claim 1, wherein the time structure of the signal waveform has a shift of the system response y (t) with respect to the excitation signal s (t) as a function of time. A part of the signal waveform is
The maximum value of the signal waveform y (t), the amplitude of the fundamental frequency of the signal waveform, the width of the waveform at half the amplitude of the maximum amplitude of the waveform signal, and / or the RMS noise of the signal waveform y (t). The method of claim 1, comprising: While exciting the transmission system (7)
The method of claim 1, wherein the at least one excitation signal is selected such that the excitation signal has a plurality of spectral lines in the frequency domain.   In the step of exciting the transmission system (7), the at least one excitation signal is selected such that the excitation signal has a fundamental harmonic spectrum line and a plurality of higher frequency harmonic spectrum lines in its frequency range. 15. The method of claim 14, wherein Exciting the transmission system (7), recording the at least one system response, and obtaining the at least one distance data are repeated in whole or in part at least once;
The method according to any of the preceding claims, wherein the modulation frequency is changed at each iteration in the step of exciting the transmission system (7).   Method according to any of the preceding claims, wherein in the step of exciting the transmission system (7), the modulation frequency greater than 10 MHz is applied.   Method according to any of the preceding claims, wherein in the step of exciting the transmission system (7), the at least one excitation signal that is periodic with respect to time is generated.   In the step of exciting the transmission system (7), the at least one excitation signal has a pulse shape, and the pulse shape is any one of a sine wave, a square, a triangle, a Dirac pulse, and a pulse group. Item 19. The method according to Item 18.   The method according to claim 18 or 19, wherein at least two excitation signals are applied to the excitation of the transmission system (7), the excitation signals having different repetition frequencies. In the step of exciting the transmission system (7), the modulation frequency is
Equal frequency interval, logarithmic equal frequency interval,
A frequency interval corresponding to a partial series of fundamental frequencies,
The frequency interval corresponding to the frequency substring by the Hibonacci number,
At least two frequency groups having equal frequency intervals,
21. The method according to any of claims 1 to 20, wherein the method is selected according to any of the following.   The method according to any of the preceding claims, wherein in the step of recording the at least one system response (5, 5 '), the frequency spectrum corresponding to the system response (5, 5') is band limited.   When exciting the transmission system (7) and recording the at least one system response (5, 5 ') for each excitation signal applied to the transmission system input, the system response (5, 5') 23. A method according to any one of claims 1 to 22, wherein the scanning is performed.   2. The step of obtaining at least one distance data, wherein the distance data is obtained directly by estimation from the signal shape and time shift of at least two system responses (5, 5 ') in the time domain. The method in any one of -23.   The method according to claim 1, wherein the step of obtaining at least one distance data obtains the distance data in the frequency domain.   26. The method according to claim 25, wherein the step of obtaining at least one distance data is based on a Laplace or Fourier transform of a time signal of the at least one system response (5, 5 ') in the frequency domain. Method.   In the step of obtaining at least one distance data, in the frequency domain, the distance data is obtained by using a probability / weighting method based on at least one noise measurement on the at least one system response (5, 5 '). 26. The method of claim 25.   28. A method according to any of claims 24 to 27, wherein system calibration is performed in the step of obtaining at least one distance data.   29. The method of claim 28, wherein in the step of obtaining at least one distance data, system calibration is performed according to an optical reference distance within the system.   30. The method according to any one of claims 24 to 29, wherein the at least one distance data is obtained by a non-linear subtraction method.   The method according to claim 25 or 28, wherein the at least one distance data is obtained by a cost function parameter optimization method.   32. The method of claim 31, wherein the at least one distance data is obtained by a cost function parameter optimization method using a maximum likelihood estimation method.   32. The method according to claim 31, wherein data from a set of at least two system responses (5, 5 ') are considered and the at least one distance data is estimated by a cost function parameter optimization method.   32. The method of claim 31, wherein system response (5, 5 ') data is considered in each case and estimated with the cost function.   Obtaining at least one distance data, transforming said at least one system response (5, 5 ') in the frequency domain and constructing a time signal (6, 6') in the subsequent time domain, and then performing an inverse transform. The method according to claim 1, wherein the distance data is obtained.   36. Method according to claim 35, wherein in the frequency domain at least two system responses (5, 5 ') are integrated into a set, whereby a time signal (6, 6') is constructed in the time domain. .   In the frequency domain, a first group of equidistant composite spectral lines is integrated to form a first time signal (6, 6 ') in the time domain, and a second group of equidistant composite spectral lines is integrated. 36. The method of claim 35, wherein a second time signal (6, 6 ') is constructed in the time domain. A device for measuring distance,
(A) comprising a signal generator for generating at least two modulation frequencies in the MHz to GHz range for excitation;
(B) comprising a transmission system, the transmission system comprising: a transmission system input unit;
A light emission source (8) for emitting light towards at least one target (3, 3a, 3b), and said at least one target (3, 3a, 3b) The object to be scattered,
A receiver (15) having a transmission system output that converts the backscattered light radiation into an electrical signal and provides a transmission system response;
(C) Estimation electronics for recording at least one system response at the transmission system output by an analog / digital converter to extract at least distance data from the waveform of the at least one transmission system response (10, 10 ', 10 ")
The signal generator has at least one direct digital synthesizer or fractional N synthesizer,
Further, the estimation electronic unit extracts distance data from a part of the waveform of the at least one system response or a time structure of the waveform of the at least one system response.
Further, the distance data is determined according to a transfer function of the transmission system evaluated from the at least one transmission system response when the distance data is extracted.
Configured as
A device for measuring distance. The transmission system has at least one parameter representing a deviation of the system response to the excitation signal, which is a function of time, i.e. a delay time of the transmission system;
39. The apparatus of claim 38, wherein the distance data is determined according to the delay time as a transition time of the light radiation coming back to the target.   40. The apparatus according to claim 38 or 39, wherein a crystal master oscillator is connected upstream of the signal generator.   41. The apparatus according to any of claims 38 to 40, wherein an electronic frequency converter for quick switching and filtering of the modulation frequency is connected to the signal generator.   42. The apparatus of claim 41, wherein the electronic frequency converter is configured as an ASIC having a frequency divider, a frequency amplifier, and a frequency switch.   43. Apparatus according to any of claims 38 to 42, wherein the signal generator is integrated with track synchronization by a voltage controlled oscillator that generates a mixed frequency for reception of a heterodyne signal.   44. Apparatus according to any of claims 38 to 43, wherein the signal generator is configured to generate a modulation frequency of about 10 MHz.   44. Apparatus according to any of claims 38 to 43, comprising an adjustable low-pass or bandpass filter on the receiving side of the transmission system output.   46. A geometer comprising the device according to any of claims 38 to 45, in particular the geometer, which is a theodolite, which simultaneously loads one or more objects (3, 3a, 3b). The above geographical measuring device capable of measuring distance.   49. A geometer as claimed in claim 46, wherein the geometer is a theodolite.   48. Geographic instrument according to claim 46 or 47, wherein a reflective member (3) is provided inside the geometer to obtain an internal reference distance.   49. A geometer according to claim 48, wherein the reflective member (3) is a reflective overcoat applied to the inside of an exit window (21) that matches the light source (8).   46. A scanner comprising the apparatus according to any one of claims 38 to 45, wherein the scanner scans and records a three-dimensional image.

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